Horizontal image translation (HIT) is an electronic process for shifting the left-eye and right-eye images horizontally as a way to alter the stereoscopic characteristics and alignment of 3D content after signals have been captured by stereoscopic cameras. When used cautiously and with full awareness of the impact on other interrelated aspects of the stereography, HIT may be used as a valuable tool in the post production process as a means to modify stereoscopic content for more comfortable viewing. HIT, for example, may be used to alter the zero parallax setting (ZPS), to compensate for stereo window violations or to compensate for excessive positive or negative parallax in the source material.
There are at least three related variables that the stereographer is continuously trying to control when shooting for a given screen size and a given viewing distance. The stereographer must use (1) the focal length of the camera lens, (2) the distance from camera-to-subject, (3) the distance between the lenses and sometimes (4) the toe-in or convergence angle of the cameras to calibrate the stereo presentation for a single screen size and viewing distance. When HIT is used downstream in the post-production process, there is a risk of unintended consequences to the chosen balance of these interrelated parameters determined by the stereographer or artist during the original production.